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https://issues.apache.org/jira/browse/HIVE-13942?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15314534#comment-15314534
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Jesus Camacho Rodriguez commented on HIVE-13942:
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Let me upload a new version of the patch before reviewing.
> Correctness of CASE folding in the presence of NULL values
> ----------------------------------------------------------
>
> Key: HIVE-13942
> URL: https://issues.apache.org/jira/browse/HIVE-13942
> Project: Hive
> Issue Type: Sub-task
> Components: CBO
> Affects Versions: 2.2.0, 2.1.1
> Reporter: Jesus Camacho Rodriguez
> Assignee: Jesus Camacho Rodriguez
>
> Introduced in HIVE-13068.
> {{(case when key<'90' then 2 else 4 end) > 3}} should not fold to {{key >=
> '90'}}, as these two expressions are not equivalent (consider _null_ values).
> Instead, it should fold to {{not NVL((key < '90'),false)}}.
> This is caused by 1) some methods still calling original _RexUtil.simplify_
> method where the bug was originally present, and 2) further improvements
> needed in _HiveRexUtil.simplify_.
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